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<TITLE>80386 Programmer's Reference Manual -- Opcode NEG</TITLE>
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<H1>NEG -- Two's Complement Negation</H1>

<PRE>
Opcode  Instruction   Clocks    Description

F6  /3  NEG r/m8      2/6       Two's complement negate r/m byte
F7  /3  NEG r/m16     2/6       Two's complement negate r/m word
F7  /3  NEG r/m32     2/6       Two's complement negate r/m dword
</PRE>

<H2>Operation</H2>

<PRE>
IF r/m = 0 THEN CF := 0 ELSE CF := 1; FI;
r/m := - r/m;
</PRE>

<H2>Description</H2>

NEG replaces the value of a register or memory operand with its two's
complement. The operand is subtracted from zero, and the result is placed
in the operand.
<P>
The carry flag is set to 1, unless the operand is zero, in which case the
carry flag is cleared to 0.

<H2>Flags Affected</H2>

CF as described above; OF, SF, ZF, and PF as described in <A HREF="appc.htm">Appendix C</A>

<H2>Protected Mode Exceptions</H2>

#GP(0) if the result is in a nonwritable segment; #GP(0) for an illegal
memory operand effective address in the CS, DS, ES, FS, or GS
segments; #SS(0) for an illegal address in the SS segment; #PF(fault-code)
for a page fault

<H2>Real Address Mode Exceptions</H2>

Interrupt 13 if any part of the operand would lie outside of the effective
address space from 0 to 0FFFFH

<H2>Virtual 8086 Mode Exceptions</H2>

Same exceptions as in real-address mode; #PF(fault-code) for a page
fault


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<B>up:</B> <A HREF="c17.htm">
Chapter 17 -- 80386 Instruction Set</A><BR>
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